This invention relates generally to spinal surgery and, in particular, to spinal cages of the type used in fusing adjacent vertebrae.
Surgeons frequently insert interbody cages in the thoracic and lumbar spine from a variety of approaches including posterior, lateral, oblique, transverse and anterior. Frequently, the disc space is degenerated and collapsed in these situations. Surgeons will often use the cage to distract the disc space as the cage is impacted into the disc space. One design utilizes a “bulleted” cage, such as the Capstone™ cage by Medtronic™. This design has a rounded wedge symmetrically disposed on the leading edge of the cage. This allows the anterior aspect of the cage to distract the disc space as it is impacted.
The problem is that such a cage has the distracting wedge shape directly in the medial aspect of the cage. With conditions such as listhesis in the setting of a collapsed disc, however, manipulation of the vertebrae from the medial aspect of the disc space is disadvantageous.
What is needed, therefore, is a mechanism which allows easier insertion of an inter-vertebral cage which also decreases the rate of end plate fracture with distraction and lessens the risk of nerve root injury with cage manipulation during the insertion process.